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基坑开挖导致地基土体整体处于卸荷状态,从而改变了抗拔桩原有的受力特点。采用数值分析方法,系统研究了基坑开挖导致的原地基中抗拔桩承载特性改变,从基坑开挖的范围、桩的相对位置等方面探讨了对桩的极限抗拔承载力、桩侧摩阻力、桩身轴力的影响规律。结果表明,开挖导致坑底以下土体卸荷回弹,在桩身上部产生正摩阻力,下部产生负摩阻力,桩身产生轴向拉力,极限抗拔力降低,减低程度与基坑开挖的规模成比例;基坑开挖所导致的群桩桩侧摩阻力与桩身轴力变化程度依次为:中心桩>边桩>角桩;群桩的遮帘作用在很大程度上影响中心桩极限抗拔承载力。
Excavation of foundation pit results in the overall unloading of soil and soil, which changes the original stress characteristics of the anti-pile. The numerical analysis method is applied to systematically study the change of bearing capacity of uplift piles in the original foundation caused by the excavation of the foundation pits. The ultimate pull-out bearing capacity of piles is discussed from the aspects of the excavation area and the relative position of the piles. Lateral friction, axial force of pile. The results show that the excavation leads to the unloading rebound of the soil below the pit bottom, resulting in a positive frictional resistance in the upper part of the pile and a negative frictional resistance in the lower part. The axial tensile force of the pile body causes the ultimate pull-off force to decrease, The scale of digging is proportional; the variation of lateral friction and pile axial force caused by the excavation of foundation pit are as follows: center pile> side pile> corner pile; the blind effect of pile group greatly influences Center pile ultimate pull-out capacity.